3.1. Sales Tax -- simple salestax.asc table

Interchange allows calculation of sales tax on a straight percentage basis, with certain items allowed to be tax-exempt. To enable this feature, the directive SalesTax is initialized with the name of a field (or fields) on the order form. Commonly, this is zipcode and/or state:

SalesTax zip,state

This being done, Interchange assumes the presence of a file salestax.asc, which contains a database with the percentages. Each line of salestax.asc should be a code (again, usually a five-digit zip or a two letter state) followed by a tab, then a percentage. Example:

Based on the user's entry of information in the order form, Interchange will look up (for our example SalesTax directive) first the zip, then the state, and apply the percentage to the SUBTOTAL of the order. The subtotal will include any taxable items, and will also include the shipping cost if the state/zip is included in the TaxShipping directive. It will add the percentage, then make that available with the [salestax] tag for display on the order form. If no match is found, the entry DEFAULT is applied -- it is normally zero.

If business is being done on a national basis, it is now common to have to collect sales tax for multiple states. If you are doing so, it is possible to subscribe to a service which issues regular updates of the sales tax percentages -- usually by quarterly or monthly subscription. Such a database should be easily converted to Interchange format -- but some systems are rather convoluted, and it will be well to check and see if the program can export to a flat ASCII file format based on zip code.

If some items are not taxable, then you must set up a field in your database which indicates that. You then place the name of that field in the NonTaxableField directive. If the field for that item evaluates true on a yes-no basis (i.e. is set to yes, y, 1, or the like), sales tax will not be applied to the item. If it evaluates false, it will be taxed.

If your state taxes shipping, use the TaxShipping directive. Utah and Nevada are known to tax shipping -- there may be others.

If you want to set a fixed tax for all orders, as might occur for VAT in some countries, just set the SalesTax directive to a value like tax_code, and define a variable in the user session to reflect the proper entry in the salestax.asc file. To set it to 15% with the above salestax.asc file, you would put in a form: